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    <title>Document</title>
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    <script>
        /**
         * 自增自减运算符：++ | --
         */
        let a = 1, b = 1, c = 1, d = 1
        console.log(a++, a); // 1， 2
        console.log(++b, b); // 2, 2
        console.log(c--, c); // 1, 0
        console.log(--d, d); // 0, 0

        console.log(++a+(++b)+(c++)+d++) // 6
    </script>
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